The present invention relates to automotive wheel pushing roller dolly""s in general. More specifically to a thermoset plastic roller dolly for use in a conveyor chain driven car wash system.
Previously, many types of dolly""s have been used in endeavoring to provide an effective means to propel an automobile through a car wash using a continuous conveyor belt. The car wash industry usually employs dolly""s with multiple rollers supporting an arm with the trailing end maintained within the track with a pair of rollers. One or more connectors attach the dolly to the continuous chain moving the dolly along the track of the conveyor system.
The prior art described below did not disclose any patents that possess the novelty of the instant invention, however the following U.S. patents are considered related:
Weiter in U.S. Pat. No. 5,140,910 teaches a dolly for pushing a automobile through a car wash having an inclined arm with a leading end located below the track and attached to the conveyor chain. A pair of track engaging rollers are positioned below the track and trailing rollers are supported by the track. The elevated pair of rollers engage the vehicle wheel with the load imparted to the track. A floating mounting engagement maintains the contact regardless of wear.
U.S. Pat. No. 4,930,424 issued to Astley is for a conveyer chain guide that includes a pusher dolly connected to a power driven endless chain. The dolly includes an upright arm that extends through and is mounted onto the track. A link interconnects the arm and chain for movement in unison. The chain guide is under the track and arranged on the longitudinal axis. Each chain guide receives the chain and maintains it in registry with the axis against lateral deflection.
U.S. Pat. No. 4,873,929 Witecki in U.S. Pat. No. 4,873,929 discloses a pusher unit that has three axles and six wheels designed for use with at car wash system utilizing a endless chain moving under a slotted track. The pusher unit uses a straight bar projecting out of the track with track contacting rollers positioned at the end of the bar. Wire engaging rollers are located at an intermediate position with the tire contacting rollers formed without internal insetting and are held in place by threaded fasteners. The under track rollers are secured to a removable axle which is mounted in a sleeve that is welded to the end of the bar. The wheels are held in place with machine screws. A second embodiment is for a hollow tubular bar using a third axle received through side holes.
U.S. Pat. No. 4,194,449 issued to Breau teaches a double dolly for use with a conveyor. The dolly has a first roller and a second support roller and a safety bar in advance of the first roller along with a frame for securing the rollers and the bar. The first roller engages the object and the second roller contacts the surface of the conveyor. The safety bar blocks the gap between the supporting surface and the first roller. The rotatability of the safety bar prevents its binding on the supporting surface in event of the dolly tipping.
In the car wash industry under track continuous conveyer chains move automobiles along a track by pushing one of the cars wheels through the washing apparatus. In this type of system a chain is attached to a dolly having multiple rollers with a support arm that includes a pair of rollers on the front that rolls along the underside of the track and a pair of rollers interfacing the top of the track. A third pair of rollers engage the automobile wheel allowing the propelling force of the chain to move the vehicle. This system is widely used and has proven to be a successful in the industry. The most manifest problem is that the dolly is subjected to substantial loads and an extremely severe environment. Further the conventional dolly""s are fabricated of a metal bar with axles welded on each end and threaded fasteners holding the wheels in place. While the operation is acceptable the dolly""s are prone to wear and because of their rigid nature are subject to fracturing and yielding usually within or adjacent to the weld joint. It is therefore a primary object of the invention to utilize a dolly that is made almost entirely of a thermoset plastic material. By the use of a structurally strong urethane plastic the dolly will not break as easy as metal since it is sufficiently resilient to allow it to deflect slightly rather than break when subjected to an overload and is much more durable. The body of the invention utilizes a urethane elastomer which can be either thermoset or thermoplastic, while either form may be employed a thermoset material of casting resins is preferred using a prepolymer and casting agents that are cast into a heated mold. After hardening the dolly body is demolded and cured.
An important object of the invention using a urethane elastomer for the dolly body is that it is extremely light in weight compared to steel, as steel has a specific gravity of 7.83 compared to urethanes 1.20, which means that the plastic is some 6 xc2xd times lighter than the welded steel body. The reduced weight permits easier handling and the shipping expense is considerably reduced.
Another object of the invention has to do with the overall expense of the complete dolly as it is cost effective relative to the all steel construction. A conventional dolly is made of two pieces of steel bar welded together with three axles at the exact locations which require a jig or fixture to maintain the necessary alignment. Cutting and welding solid steel bar stock is time consuming. Also drilling and tapping six places is labor intensive as the operation is normally accomplished on a single piece basis. The cost of a mold can be amortized over a long period of time and the material cost of the urethane elastomer is less to start with than the metal. All in all the invention is indeed a cost tremendous cost saving to the operator of a car wash equipped with the under chain conveyer and also to the original equipment manufacturer since multiple dolly""s are required with each system.
Still another object of the invention is realized in using a unitary dolly body since there are no welds to crack or break, further the steel axle, in the past, has had a tendency to wear near the support bar where the roller continually rotates. The invention has no such welds and the urethane elastomer is formulated to be self-lubricating as well as handling shock and vibration loads thus eliminating the wear between the roller and the axle.
Yet another object of the invention is in the addition of a gusset for added strength as it will handle more weight and it flexibly yields instead of fracturing. It has been anticipated that the load capabilities would exceed 12,000 pounds (5,448 kg). The location of the gusset is in direct alignment with the front and second, or upper axle, which transfers the load linearly therebetween in tension offsetting the cantilever load of the prior art.
A further object of the invention is the ease of attaching the rollers with a snap ring. The use of a snap ring, or more precisely a retaining ring, in a groove within the distal end of each axle is easy to accomplish with common internal retaining ring pliers. To assure that the ring stays in place a secondary securing means is provided in the form of flat round push nut that simply slides over the axle and holds firmly with a plurality of barbs under tension gripping the peripheral surface of the axle.
A final object of the invention its non corrosive nature, since both the dolly body and rollers are fabricated of a material that is impervious to oxidation in the form of rust and it is inert to most chemicals, at least the type found in the car was environment. The only metallic components are the retaining rings and the push nuts both of which are stainless steel.